Wait for runnables to start up in tst_QThreadPool::cancel()

In order to get reproducible runs of the test, we need to
wait in the main thread until all runnables have started
executing. Otherwise, what the cancel() loop below actually
does will vary from run to run.

Change-Id: Ib912b0943e7bbd55c9480ae6fd4011ba20ac457e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/tests/auto/corelib/thread/qthreadpool/tst_qthreadpool.cpp b/tests/auto/corelib/thread/qthreadpool/tst_qthreadpool.cpp
index dede0be170..152aa4abdd 100644
--- a/tests/auto/corelib/thread/qthreadpool/tst_qthreadpool.cpp
+++ b/tests/auto/corelib/thread/qthreadpool/tst_qthreadpool.cpp
@@ -958,16 +958,19 @@ void tst_QThreadPool::clear()
 void tst_QThreadPool::cancel()
 {
     QSemaphore sem(0);
+    QSemaphore startedThreads(0);
+
     class BlockingRunnable : public QRunnable
     {
     public:
         QSemaphore & sem;
+        QSemaphore &startedThreads;
         QAtomicInt &dtorCounter;
         QAtomicInt &runCounter;
         int dummy;
 
-        explicit BlockingRunnable(QSemaphore &s, QAtomicInt &c, QAtomicInt &r)
-            : sem(s), dtorCounter(c), runCounter(r){}
+        explicit BlockingRunnable(QSemaphore &s, QSemaphore &started, QAtomicInt &c, QAtomicInt &r)
+            : sem(s), startedThreads(started), dtorCounter(c), runCounter(r){}
 
         ~BlockingRunnable()
         {
@@ -976,6 +979,7 @@ void tst_QThreadPool::cancel()
 
         void run()
         {
+            startedThreads.release();
             runCounter.fetchAndAddRelaxed(1);
             sem.acquire();
             count.ref();
@@ -995,11 +999,14 @@ void tst_QThreadPool::cancel()
     QAtomicInt dtorCounter = 0;
     QAtomicInt runCounter = 0;
     for (int i = 0; i < runs; i++) {
-        runnables[i] = new BlockingRunnable(sem, dtorCounter, runCounter);
+        runnables[i] = new BlockingRunnable(sem, startedThreads, dtorCounter, runCounter);
         runnables[i]->setAutoDelete(i != 0 && i != (runs-1)); //one which will run and one which will not
         threadPool.cancel(runnables[i]); //verify NOOP for jobs not in the queue
         threadPool.start(runnables[i]);
     }
+    // wait for all worker threads to have started up:
+    QVERIFY(startedThreads.tryAcquire(MaxThreadCount, 60*1000 /* 1min */));
+
     for (int i = 0; i < runs; i++) {
         threadPool.cancel(runnables[i]);
     }